Lamps of the type described are known in the art. An exemplary lamp is the mercury discharge type. In such lamps light is produced by the passage of an electric current through mercury vapor. These lamps usually employ an outer envelope containing an inert gas or vacuum. An arc discharge tube is mounted within the outer envelope and contains first and second spaced apart main electrodes. The arc tube is hermetically sealed and contains the requisite amount of mercury together with a readily ionizable gas, such as argon, to improve starting.
To further improve starting performance, commercially available high pressure mercury lamps employ a starting probe which is an electrode sealed into the lamp adjacent to one of the main electrodes and electrically connected to the other of the main electrodes through a current limiting resistor.
In a low wattage mercury lamp application a ballast is employed which uses standard line voltage (120 V A.C.) connected through a current limiting inductance directly to the mercury lamp. This ballast provides a high voltage-low energy pulse which is sufficient to break down the gap between the main electrodes and, thus, no starting probe is required. It would be an advance in the art however, if better starting and better lumen maintenance could be provided for electric discharge lamps of the low wattage type.